This supplementary proposal is for a two year extension of the Chemical Transducer Laboratory in the Biomedical Electronic Resource (Grant No. RR 00857) to have the same expiration date as the rest of the Biomedical Electronics Resource. The goal of the Chemical Transducer Laboratory is to conduct research and development of solid state chemical and biochemical transducers. The specific aims are: (1) Basic Research: To study the behavior of electrolyte-insulator-semiconductor (EIS) interface behavior; to develop analytical models for the ion sensitive field effect transistors (ISFET) as the concentration of primary sensing ions and other supportive electrolytes varies; to investigate mechanisms that can alter the chemical selectivity of the insulator surface, leading to the development of improved pH sensors as well as new sensors. (2) Sensor Development: To investigate the chemical response of different insulating materials in the ISFET structure, including Al2O3, to improve sensitivity, selectivity and baseline stability; to design manufacturable pH sensors with planar surface and back contact; to develop multichannel ISFET with on-chip processing circuits; to improve the packaging of ISFET pH sensors. (3) Supporting Functions: To develop computer controlled CV measurement techniques for EIS and sensor research; to establish a data base for the characteristics of ISFET using SEM, Auger spectroscopy, and other facilities; to provide pH sensors for local and national collaborative projects.